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# Sound Perception

### Sound and its Perception, Acoustics, Decibels

Question | Answer |
---|---|

to-and-fro motion of an object is defined as | oscillation |

vibration transferred from air particle to air particle is usually called | sound |

disturbance of molecules that propagates (moves) through a medium is | sound |

substance through which sound travels, such as air, water, steel, bone is called a | medium |

movement of a disturbance of molecules through a medium is called | propagation of sound |

molecules displaced a very small distance from where they want to be (equilibrium position) is a | disturbance of molecules |

this is where the net force is zero | equilibrium position |

a kind of vibration where the oscillations repeat themselves at same rate over and over again like a pendulum is called | simple harmonic motion |

when oscillation dies down the dying of vibrations over time is called | dampening |

if you increase volume you increase | pressure (like air in tire) |

if you decrease volume you decrease | pressure |

state of lower than ambient pressure (pressure is maximally negative) | rarefaction |

state of positive air pressure or molecules pushed together creating more dense space is called | compression (condensation) |

a sudden short sound that doesn't last long is known as a | transient sound (ex: slamming of door or an unvoiced sound such as "sss...") or impulse sound |

when sound source is farther away and its a few seconds before you hear the sound, this is because | speed of light is faster than sound |

speed of sound is related to | elasticity and density of the medium |

speed of sound is equal to | C (speed of sound) |

the restorative force, which can be thought of as the ability of a substance to resist deformation is called | elasticity (E) |

the amount of mass per unit volume is known as | density (D) |

broccoli has greater _______ than the Oregonian rubber band, because it won't deform as easily | elasticity |

the greater the elasticity the greater the | speed of sound |

increase elasticity | increase C |

increase density | decrease C |

air is less dense as we increase | temperature |

as gas expands density | decreases |

speed increases with temperature because gas expands as temperature | increases (and molecules move quicker) |

steel and water are more ______ than air | dense |

helium is less _____ than air, so sound travels ______ through it than air | dense, faster |

CO2 is more ______ than air, so sound travels ________ through it than air | dense, slower |

water and steel are more dense than air, so sound travels _______ this is because of elasticity (the dominant factor) | faster |

compressions and rarefactions move from ________ to ______ | sound source to reciever |

vibration that repeats itself | periodic vibrations (ex: guitar string or "aaaa") |

vibration that doesn't repeat itself | aperiodic vibration (ex: door slamming, "sssss") |

single complete execution of a periodically repeated phenomenon | cycle |

measure of magnitude of a sound/vibration | amplitude |

time it takes to complete one cycle | period |

number of cycles per second | frequency |

how fast something is vibration is known as | cps=cycles per second |

F= | 1/period (1/T) (Unit: Hz) |

T= | 1/F (Unit: sec) |

velocity= | displacement/time (30miles/1hr) |

pressure= | force/area |

the greater the force, the greater the _______ | pressure |

psi stands for | pounds per square inch |

in the metric system the unit for force is | Newton's |

1 Pa= | N/m2 |

Force= | mass times acceleration (F=ma) |

amount of force required to cause a mass of 1 Kg to accelerate to 1 meter/squared sec (1m/s2) is | Newton |

the distance btwn successive condensations and rarefactions is the | wavelength |

the faster the speed of sound the _______ the wavelength (lower frequency) | larger |

the smaller the wavelength the higher the | frequency |

wavelength= | speed of sound/frequency (wavelength=c/f) |

2 sinusoids with same frequency, only _______ changes and gets larger/higher | amplitude |

hearing nothing, like noise cancellation headphones is called | total cancellation |

different frequencies combined together make a | complex waveform |

any waveform that is not a sinusoid is a | complex waveform |

wave that repeats itself | periodic waveform |

even integral number multiples of a frequency | harmonic |

the largest common multiple of a series of sinusoids | fundamental frequency |

With frequencies of 150Hz, 250Hz, 350Hz what would the fo be and the 2nd and 3rd harmonic? | fo=50 (1st harmonic), 2nd harmonic=100, 3rd harmonic=150 |

Given frequencies: 125, 250, 375, 500Hz what is the fo? and the H3? | fo=125Hz (Ist harmonic), H3=375Hz |

300Hz is or below is cancelled-the difference in pitches, this is called | the case of the missing fundamental |

Fo of a mans voice is= | 100Hz |

Fo of a females voice is= | 175-200Hz |

a straight line of a sinusoid that shows what frequencies are present is known as a | spectrum |

mathematical procedure that coverts and breaks waveform down by means of frequencies (from time domain>frequency domain) | Fourier Analysis |

most vibrations are | aperiodic |

top of the peaks on the spectrum graph are known as | formants (each vowel has it's own pattern of formants, so when we change shape in tongue, they change frequency) |

the faintest sound human ear can detect | 20 microPa=.00002Pa (very small change in pressure) |

the loudest sound human ear can detect | 20,000,000 microPa=20Pa |

the power to which 10 has to be raised, to equal that number | log10 |

log10^1= | 0 |

log10^10= | 1 |

log10^1000= | 3 |

log10^1,000,000=log10^6= | 6 |

log10^4=4= | log10^10,000 |

P1/Po | Pressure/Reference Pressure |

SPL stands for | Sound Pressure Level |

the logarithm formula we use is: 20logP1/Po (Po=.00002 Pa, standard measure point for SPL) | we use this to calculate the dB SPL or dB of the pressure of a sound or sounds. |

The pressure of sound A=.035 Pa. The pressure of sound B=.0075 Pa. How many dB is sound A above sound B? | 13.38 dB (not dB SPL, because need 20 mPa=.00002 Pa) |

The pressure of a sound is .44 Pa. How many dB SPL is this? | 86.85 db SPL |

If sound A is twice the pressure of sound B, there is a ____ dB difference. | 6 |

Pressure of sound a IS 10 times the pressure of sound B. How many dB is A above B? | 20 dB |

Pressure of sound A= .00002 Pa and pressure of sound B= .00002 Pa. How many dB is A relative to B? | 0 dB SPL (As long as they're the same, you get 0 dB) |

If you combine dB from multiple sound sources, such as 80 dB SPL and 80 dB SPL, you get a _____ dB SPL increase. | 86 dB SPL (80 dB SPL + 6 dB) |

if waveform of 2 sounds are identical aka same frequency, you get a doubling of sound ______ | pressure |

There are 2 tractors in a field both with 90 dB SPL, one starts its engine and then the other. What is the combined dB SPL? | 93 dB SPL, because free field, no reflection of buildings or trees because empty space outside. |

80 dB SPL + 6 dB= | 86 dB SPL |

Two or more dB values of different sounds can look the same, but are not necessarily the same unless they have the same ______ ________ | reference pressures |

power=energy flow= | watts |

intensity=energy flow/unit area= | watt/m2 |

faintest sound intensity (at 20mPa pressure)= | 10^-12 w/m2 |

anytime you have fraction such as .42, the answer is going to be | negative |

energy flow, energy expanded per unit time watts is | Power |

energy flow per unit area aka power speed over a given area is | Intensity |

Power/area= | watt/m2 |

Unit of measurement for dB with intensity is I1/Io and has a unit value of | dB IL (as long as ration of 2 intensities) |

opposition to energy flow | impedance |

energy lost in the form of heat | resisitance (friction) |

energy is stored | reactance |

if you have a spring that is opposing and continues to compress you have more and more potential energy created, which is then stored in the string, which is called _______ _______ | compliant reactance (opposition to force, potential energy stored |

opposition to force, energy stored in motion, kinetic is | mass reactance |

what are the two types of impedance? | resistance and reactance |

what are the two types of reactance? | mass reactance and compliant reactance |

When P1 | negative (this is because the log of a fraction is negative) |

P1=Po there are ____ decibels. | zero (because the logarithm of 1 is zero) |

If the pressure of one sound source is twice that of another, it is ___ dB greater than the second sound. | 6 db (This is because 20log10^2=6dB) |

combining two sounds with exactly the same waveforms will result in ___ the pressure of one sound alone. | twice |

If the time waveforms of two sounds are not equal, combining the sounds will not _____ the pressure. For example, two machines, each producing 70 dB SPL will together produce 73 dB SPL. That is, there will be an increase of only __ dB. | double, 3 dB |

dB SPL - dB = | dB SPL |

dB SPL + dB = | dB SPL |

dB SPL - dB SPL = | dB |

If Po is not .00002 Pa, then the unit is not | SPL |

Express the number 10,000,000,000 in exponential form. | 10^10 |

What is the logarithm base 10 of 10,000,000,000? | log10=10 |

T/F Zero dB means that no sound is present. | False |

T/F 20mPa corresponds to .00002 Pascals. | True |

T/F The unit of intensity is the watt. | False, it is watt/m2. watt is the unit of power. |

T/F For a given sound source, sound pressure in a room depends on the size of the room. | True |

Created by:
rcheek